Monday, November 13, 2006

Grazing with Goats to Biologically Control Amaranthus spinosus.

Christy Gustafson, Delaware State University, 1200 N Dupont Hwy., 1200 N Dupont Hwy., Dover, DE 19901, United States of America

Weeds with defense mechanisms to prevent herbivory can become a major nuisance in a pasture.  A weed that is becoming a pest in many Delaware pastures is Amaranthus spinosus (spiny amaranth).  Even though A. spinosus may have good nutritive value, the plant has prickly spines at the axils of the leaves and branches, making it undesirable to the majority of wild and domestic herbivores.  With environmental concerns and increasing costs of chemical control methods, more biological control techniques are being utilized.   Goats (Capra hircus Linn.) are known to tolerate or even select vegetative material and weeds that may not be palatable to most production animas, which make them a desirable weed control animal.  Goats are great for grazing with other livestock in a mixed grazing system, utilizing plants that other herbivores will not and improving the availability of nutrients to desirable plants.  The objective of the study was to determine if the goats would consume A. spinosus and if the plants were more desirable at various stages of growth.  Two Tall Fescue pasture at Hickory Hill Forage Research farm in Cheswold, Delaware, were used to carryout the study.  Quadrants were placed throughout each pasture and height measurements and stages of development of the A. spinosus were recorded before and after the goats grazed to determine the amount and type of plant material consumed.  The height measurements post grazing, ranging from 2 cm to 21.5 cm, showed that the goats consumed large portions of the plants in the pre-bloom and bloom stages.  Goats ate the A. spinosus and seem to prefer the plant in more mature stages of development.  Further chemical analyses of the plants are being performed to determine nutritive values and possible toxins at the various stages of growth.